Opioid misuse and addiction are significant and increasing problems in the United States. Opioid agonist therapy (OAT) with sublingual buprenorphine became available in the United States in 2003 and has significantly expanded access to and participation in opioid agonist treatment. The Substance Abuse and Mental Health Services Administration (SAMHSA) published treatment guidelines to support practitioners providing this new treatment, but early studies suggest significant variations in practice patterns and only modest adoption of recommended practices. The purpose of this study is to utilize administrative data to evaluate the quality of buprenorphine treatment for Medicaid beneficiaries. Our specific aims are: 1) to describe to what degree current treatment adheres to the treatment guidelines; 2) to determine which patient level factors such as age, gender and medical and psychiatric co-morbidities are associated with receiving higher quality care, and; 3) to investigate if receiving care according to treatment guidelines is associated with retention in treatment or future utilization of high intensity substance abuse treatment services. For aim 1, we will describe what percentage of Medicaid beneficiaries who were prescribed buprenorphine received outpatient physician visits, outpatient behavioral health treatment, laboratory screening for liver disease, drug testing and medication dosing at the levels recommended in the guidelines. For aim 2, we will rely on logistic and Poisson regression to explore whether meeting these quality indicators is associated with patient level factors. Finally, for aim 3, using Cox proportional hazards models we will measure the association between receiving care according to treatment guidelines and outcomes such as treatment retention and future treatment service utilization. The study will include approximately 12,400 Medicaid beneficiaries who received buprenorphine for opioid addiction between 2003 and 2009. It will be the first study to explore the use of administrative data to assess the quality of buprenorphine treatment. Because both the number of people addicted to opioids and the rates of participation in buprenorphine treatment are expected to rise, this information will be essential to Medicaid program managers and policy makers working to provide access to treatment while maintaining quality and controlling cost.